Art of preparing coal for market



Patented Mar. 26, 1935 UNITED STATES PATENT OFFICE No Drawing.Application July 8, 1933, Serial No. 679,573

Claims. (Cl. 209-2) My invention refers to preparation of coal, moreparticularly to facilitating the individual operations involved inpreparing coal, to reducing cost of such operations and to improving the5 coal output.

Coal as mined is an unassorted aggregate consisting of all sizes, fromthe largest pieces "that one man can lift to finest dust. Within thisaggregate is pure coalalong with natural impurities which lnust beremoved. These impurities occur interbedded in the coal veins and,within the mine, cannot be advantageously removed.

Near the mine mouth a surface plant is normally provided wherein thecoal as mined is prepared for market. In the preparation plant, the massof mixed material is first usually assorted into size classclassifications such as will best allow application of the various meansavailable for separating marketable coal from impurity. The naturalimpuritiesassociated with coal are chiefly slate and bone", pieces ofinterlaminated slate and coal.

The means most frequently employed in removal of impurities are: (1)Hand picking, applicable to larger sizes and pieces, (2) jigging,adapted to sizes and pieces, ponderable, but too small for successfulhand picking, (3) air'cleaning, adapted to all sizes smaller than can behand picked and (4) wet concentration, adapted to segregations of smallparticles. These treatments, and indeed any normal handling of coal inits progress from the mine t6 the consumer, involve agitation ortumbling of a coal mass containing assorted coal sizes.

As at present marketed, well sized coal is in greatest demand, and, ingeneral, larger sizes.

command a higher price than small sizes, which latter are known in thetrade as slack and will pass through a screen having 1 inches or smallermesh. Profitable production depends upon a minimum of degradation oflarger into smaller sizes.-

In coal preparation plants, necessary chuting and sliding arrangementsare often such as to impede proper'flowage of coal, either because ofinsuilicient slope or corrosion of sliding surfaces. Also, oftencoal ispassed through spouts or gates too restricted to allow at all times freedelivery. Whatever facilitates chuting and spouting speeds production.

Cost of operating a coalpreparation plant is a function of capacity.Increasing plant capacity correspondingly increases realization.

My invention improves coal preparation by affording better screening,jigging, dry cleaning,

wet concentration and facilitating hand picking.v It lowers cost ofplant operation both by increasing output and eliminating dust. Itallows flatter chuting' and freer spouting. It increases coalsalability. It ,increases realization by raising the proportion oflarger sizes.

My invention consists in applying to an aggregate of intermixed coal andimpurity composed predominantly of pieces larger than slack and which isto be subsequently treated in order to separate the commercial coal fromassociated impurity, or to clean coal still in process, a dosage of oilslightly in excess of that required to form, throughout the mass, adust-laying fllm upon the coal. By 'oil, I mean any substance of an oilycharacter fluid at 200 degrees Fahrenheit. Oil alone is effective inobtaining practical results. However, I prefer to apply the oil as anoil-in-water emulsion and use, normally, a soap formed emulsion, as thepresence of soap lowers surface tension and, in itself, is a lubricatingagent.

In the appended claims the term an oily liqui is used to designate andto include both oil and oil emulsions or like liquids containing oil.

. The oil, having an aflinity for coal, attaches itself to the coalelement. of the mass and, in hand picking, serves to emphasize thedifference in appearance between rock, bone, and coal, therebyfacilitating this operation.

In screening, the beneficial effect of oiling is particularly noticeablein small sizes, especially where thecoal as mined is wet. Lubricatedpieces, sufficiently small 'to pass through screen openings, do soreadily, while those which enter screen openings but are unable to passthrough, free themselves instead of remaining to be sheared or broken bythe passage of unenmeshed material as occurs when unoiled coal isscreened. Thus, due to oiling, screen capacity is increased anddegradation reduced. 7

In jigging, the surface lubricated coal frees itself more readily andstratifies, more quickly than will coal unoiled.

In dry cleaning, oiling increases uniformity of air passage and speedsseparation of coal from impurity. Also, the riflles which are providedfor guiding the impurities do not impede coal travel, surfacelubrication allowing the coal to slide over the riflies. The lubricatedcoal particles free themselves from'the aggregate more readily thanwould the same particles unoiled. The presence of a slight excess of oilkeeps the riflies polished and the air permeable deck from becomingchoked with dust.

In wet concentration, separation of coal from impurity occurs quicklyand completely where coal particles are surface lubricated. Also, theoil coated particles slidefreely over the riflling.

In chuting, surface lubrication allows fiatter angles than is possiblewhere coal is unoiled. Also, the slight excess of oil reduces corrosionand keeps metal surfaces in good condition. In passing oiled coalthrough restricted openings, arching, the chief cause of stoppage, doesnot readily occur.

The coal surfaces, immediately upon their becoming filmed with oil,accumulate a thin, permanent layer of dust, appreciably increasingWeight of larger, higher realization sizes, and removing from the smallsizes very fine dust the presence of which is not desirable. This dustlayer, apparent under a microscope, on the oil-coated surfaces of thelarger coal sizes, results not only in recovery in the most valuablesize classification of combustible coal dust heretofore lost, but formsa protective coating on the larger coal pieces which reduces breakage ofthese pieces from impacts to which they are subjected in the coalpreparation process. At the same time, the removal of this dust from thesmaller or slack size coal results in a superior slack which burns witha higher combustion rate because of minimizing of dust pockets andair-channeling. This result of my treatmentis not accomplished bytreatment of slack with oil subsequent to its preparation, as suchtreatment merely lays the dust Without transferring it from the slack tothe larger size classifications. The terms size or size classificationare to be understood as referring to commercial size classificationssuch as lump, slack, etc., and these terms do not merely mean that coalis present in particles of differing size but substantially all in thesame commercial size classification.

In prevention of escape into the air of dust from the aggregate inprocess of treatment, best efiects are obtained where the dosage of oilis applied early in the treatment; normally at the point where the minedmaterial is delivered into the preparation plant. Also, by applying at,this point, maximum opportunity is afforded for the oil to spreadthroughout the mass and dust elimination is complete. However, I do notconfine the applicability of my invention to the entire aggregate asmined. My invention applies to oil dosage of the mined aggregate as awhole or to any subdivision of the mined aggregate ahead of anydepartment of preparation or to cleaned coal in process, as forinstance, in rescreening, chuting or spouting cleaned coal.

Having described my invention and its application, I claim:-

1. In a process for treating coal, the steps which comprise applying adosage of an oily liquid to a run-of-mine coal containing predominantlysizes larger than slack, and subsequently removing impurities andassorting it into commercial sizes with adhering fine elements.

2. In a process for treating coal, the steps which comprise applying adosage of an oily liquid to a subdivision of a run-of-mine coalaggregate containing predominantly sizes larger than slack, andsubsequently removing impurities and assorting it into commercial sizeswith adhering fine elements.

3. In a processfor treating coal, the steps which comprise applying adosage of an oily liquid to a run-of-mine coal aggregate containingpredominantly pieces larger than slack and causing thereby fine elementswithin the aggregate to adhere to oiled surfaces of larger pieces andparticles and subsequently removing impurities.

4. In a process for treating coal, the steps which comprise applying adosage of an oily liquid to a subdivision of a run-of-mine coalaggregate containing predominantly pieces larger than slack and causingthereby fine elements within the aggregate to adhere to oiled surfacesof larger pieces and particles and subsequently removing impurities.

5. In a process for treating coal, the steps which comprise applying adosage of an oily liquid to a run-of-mine coal aggregate containingpredominantly sizes larger than slack and subsequently assorting it intosize classifications with adhering fine elements.

6. In a process for treating coal, the steps which comprise applying adosage of an oily liquid to a subdivision of a run-of-mine coalaggregate containing predominantly sizes larger than slack andsubsequently assorting it into size classifications with adhering fineelements.

NOEL CUNNINGHAM.

